package chapter04.field_method05;

public class Circle{
    double r;
    public void area(){
        double pai = 3.14;
        double s = pai * r * r;
        System.out.println("面积为:" + s);
    }
    public void area2(double pai){
        double s = pai * r * r;
        System.out.println("面积为:" + s);
    }
    public double area3(double r,double pai){
        double s = pai * r * r;
        return s;
    }
}

